Hearing assistance devices are electronic devices that provide better listening for wearers. One type of hearing assistance device is a hearing aid. Hearing aids provide signal processing functions such as noise reduction, amplification, and tone control to correct for an individual's own hearing loss. Performance of a user's hearing aid, while in the user's ear, is difficult to measure. However, such measurements may enable better programming of a user's hearing aid because each user's ear is different.
Various prescriptive fitting formulae can be used to calculate custom targets for the hearing aid response. A goal of the fitting is to adjust the gain of the hearing aid so that its output in the patient's ear matches the prescribed targets. This is referred to as target matching. Accurate target matching enhances audibility and comfort for the patient in a variety of listening environments. It is desirable to accurately and quickly perform target matching. It is further desirable to not use extra equipment or a model of hearing aid response to perform the target matching.
Some known target matching methods do not automatically adjust gain. Known target matching methods that automatically adjust gain rely on a model of the hearing aid response. Standalone real-ear measurement systems allow the audiologist to overlay the measured hearing aid response on a desired target curve, and then manually adjust gain settings until the response matches the target. This process usually requires several adjustment-measurement iterations in order to get the response to match the target for multiple input levels. This method is time consuming and inconsistent from user to user. Hearing aid manufacturers' fitting software automatically adjusts gain, but rely on a model of the hearing aid response rather than a measurement to determine the accuracy of the resulting target match. Several factors contribute to the accuracy of the model, and thus the accuracy of the target match. These factors include: differences between the typically-modeled nominal 2 cc coupler response and the actual device response; the accuracy of the transfer functions applied to the 2 cc coupler response to obtain a predicted real ear response (the average ‘real-ear-to-coupler difference’ (RECD) and the free-field-to-mic effect). A custom-measured RECD may be used to improve the accuracy of this model. The RECD can be measured using a standalone system and then transferred to the software, or it can be measured using an on-board hearing aid measurement which is then automatically integrated into the fitting software.
There is a need in the art for improved systems to assist in measuring the performance of a hearing assistance device while the device is in the user's ear.